Please Help Sync my Calendar!

I want to find a simple inexpensive way to keep my calendar in sync with my assistant back in my office (I don't have Exchange). Presently we use Yahoo calendar, but there's got to be a better way now that I have a 650, right? Is there a calendar program that stays in sync when either of us makes changes much like, say, Chatter does for email? Anyone have any ideas? Much appreciated.

sproqit.com
the best product at this time, you can input calander meetings or change them and right away it will show up on the outlook calander software, and the same thing for your assistent when they inputing or changing any thing in their calander its changing on your palm.
they have monthly charge of $8.95 per month